I may be incorrect, but my understanding is that in a heavy multi user environment, if you have
QualCols set to 10 you might be seeing a lot of "resources not available" conflicts. I.E. user 1 does an update and locks up an entire page of data instead of just the one row being updated. Anyone else accessing the database and happens to select a row in the same page that user 1 has locked will not have access until user 1 releases it. QualCols 2 would be that user 1 locks only one record thus user 2 would not get locked out unless they access the exact same record. So if your app is unlikely to access the same "page" of data for updating, even in a heavy multi user environement, then QualCols 10 would be OK. If your app is constantly updating the same table and likely records that are in like pages, then QualCols 2 would reduce the number of access conflicts greatly. So it all depends on what your app is doing. If only performing looks ups and entering new data 95% of the time, then QualCols 10 is probably the way to go. If a large number of users are accessing the same data for updates, the QualCols 2 probably is the way to go. As Razzak mentioned, this can be set "on the fly". However, I must assume that the effect is global. I.E. is user 1 sets QualCols to 10 and does an update, they will lock out pages of data. Even if user 2 has QualCols 2 (locks single rows) if they try to access data that is in the page of user 1, they will be locked out until the user 1 update completes. So with all things programming, one must evaluate the environment the app (or command) is going to be used. A scheduled command that runs at 2:00am with no one else on the system could/should have different settings than one running at 10:00am when a hundred users are connected. An app that is 95% new data entry or lookup would have different settings than an app that is 95% data maintenance. The QualCols in my opinion is a switch that is available for fine tuning. An update on a single record that uses an index column and a where clause will not have any speed difference if QualCols is set to 10 or 2. An update on 100,000 records without a where clause will have a magnitude difference. So again, it depends on what your app is doing. Hope that helps. -Bob ----- Original Message ----- From: [email protected] To: "RBASE-L Mailing List" <[email protected]> Sent: Wednesday, November 4, 2009 8:49:10 AM GMT -06:00 US/Canada Central Subject: [RBASE-L] - Re: Qualcols 2 vs 10, what do you giveupbychangingfrom 2 to 10? Bob: Thanks for the testing! Since qualcols 10 is the default, your results show that you should not change it to 2 if you're going to be making table updates that affect a bunch of rows. So... now I'm even more confused. I'm assuming that most people are running with qualcols 10 since it's the default (me included). The problem presented was how to speed up certain functions. Since qualcols 10 makes big operations much faster, wouldn't that be what you're concerned about? Why would you need qualcols 2 if perhaps that only works on smaller targeted sets of data? What am I missing? Karen Very interesting and impressive! Tested on 100mb network. Database on file server and commands executed on work station. Feedback set to on for both tests. Test table has 100,900 rows (no indexes) Qualcol = 10 Update testtable set ItemStatus = 'Update Test 1' total update time = 3.672 seconds Same table, same test except QualCol = 2 Update testtable set ItemStatus = 'Update Test 2' Total update time = 8 minutes 24 seconds. That is a significant difference! -Bob Very interesting and impressive! Tested on 100mb network. Database on file server and commands executed on work station. Feedback set to on for both tests. Test table has 100,900 rows (no indexes) Qualcol = 10 Update testtable set ItemStatus = 'Update Test 1' total update time = 3.672 seconds Same table, same test except QualCol = 2 Update testtable set ItemStatus = 'Update Test 2' Total update time = 8 minutes 24 seconds. That is a significant difference! -Bob
